Calcium oxide

Endpoint summary

Description of key information

Human data support the finding that effects of burnt lime (CaO) are limited to the external surfaces of the body (local irritation) and no systemic effects are anticipated. If inhaled, the critical effects of lime dust can be expected to be sensory irritation and a decrease of lung function parameters at long-term exposure.
Calcium supplementation during pregnancy is not adverse, but instead may be beneficial both to the mother and to the offspring.
Calcium appears to reduce the risk of recurrent colorectal adenomas
Toxicokinetics of calcium has been investigated in a range of human studies, which are further referred to in section 7.1.1 of the technical dossier.
Case reports underline the irritating properties (skin and eye) of CaO/Ca(OH)2.

Additional information

Studies summarised in section "Health surveillance data" report individual cases or epidemiological data regarding human exposure to lime (or cement as surrogate for the alkaline effects of lime). Cain (2004), Torén (1996), Lahaye (1987), Wegman (1991), Vestbo (1991), Fell (2003), Yang (1996), and Eid (1969) form the basis of the SCOEL recommendation of occupational exposure limits (inhalation). Cain (2008) is provided as a supplementary reference to Cain (2004), confirming the nature of effects upon short-term exposure to CaO, which are described as sensory irritation and slightly increased secretion from the nasal mucosa. Meo (2003), and Al-Neaimi (2001) are provided as additional references describing typical symptoms of long-term over-exposure to cement dust, typically being reduced pulmonary function, pleural thickening and chronic bronchitis.

Villar (1990), Levine (1997), Koo (1999) are used as supportive data for the endpoint "developmental toxicity/teratogenicity" (section 7.8.2 of the technical dossier), demonstrating either a beneficial effect of lack of adverse effects of calcium in pregnancy, both to mothers and their offspring.

Belizán (1991) reports a protective effect of calcium against hypertensive disorders in pregnant women.

Baron (1999) reports that calcium supplementation is associated with a significant - though moderate - reduction of the risk of recurrent colorectal adenomas.

The references Johnston (1992), Lloyd (1993), Elders (1994), Reid (1993), Moser-Veillon (2001), Rosado (2005), Wastney (2000), Braun (2008), Minihane (1998), Sokoll (1992), Kalkwarf (1998), Peacock (2000), Dawson-Hughes (2002), and Bonjour (1997) are dealing with toxicokinetic parameters of calcium and are therefore reflected in section 7.1.1 of the technical dossier (basic toxicokinetics), together with SCF and FAO/WHO documents in a weight-of-evidence approach.

No relevant classical epidemiological data have been identified.

In section 7.10.3 of the technical dossier, Hahn et al. (2002) represents a German governmental report of chemical burns due to accidental exposure (both occupational and general population) to building materials consisting of or containing lime. Causes of eye exposure to lime (calcium hydroxide and oxide) are reviewed by Grant (1986). A further study reports a human case of eye irritation due to accidental exposure to calcium hydroxide (Schmidt, 2008).

Overall, this human case study demonstrates that exposure to hydrated lime may result in severe eye irritation. Sheikh (1987) and Bo-Linn (1984) are provided as supportive information for deriving toxicokinetic information (oral absorption of calcium) and are therefore referred to in the section "basic toxicokinetics".

No data on sensitisation in humans were retrieved.

Relevant exposure-related observation (section 7.10.5 of the technical dossier) other than those addressed in section 7.10.1 and 7.10.3 of the technical dossier were not identified.